Waviness in the finish, what causes it and other questions.

[Edward]

OK, in search for an answer, I've found some youtube videos that illustrate typical examples of chatter.

https://www.youtube.com/watch?v=LTIEXLE9dH8
https://www.youtube.com/watch?v=U74NzmPrzeo
https://www.youtube.com/watch?v=QaIVvd2wFOM

As said above, I've only experienced that kind of high frequency nasty chatter noise when squaring the end side of 40mm extrusions, which is understandable, due to the vibration of the unsupported inner shape of the profile, and maybe deflection of the long endmill needed to machine this.

I've also seen videos of how chatter can affect the finish, kind of curly marks on the surface. But my initial post above with the photo of the wavy surface pattern seems different in shape, as these are vertical spaced lines. I certainly didn't hear any chatter when cutting, but perhaps there was some sort of vibration or lack of rigidity?
Any clues please?


Edward